SHUTDOWN_MSG:/************************************************************SHUTDOWN_MSG: Shutting down DataNode at CMSCVCHEPOC001.techmahindra.com/172.18.98.93************************************************************/

Re: Datanode is not starting

The fatal message is more interesting than the warning. It's complaining about incompatible cluster ids.

Are you adding a datanode that already has data in the data dir on local disk? The data there probably has a conflicting cluster id. You should probably delete the local data dir(s) (or move them out of the way).

Re: Datanode is not starting

Data directory is local filesystem storage location for each datanode in your cluster. Search for "dfs.datanode.data.dir" property in hdfs-site.xml file to find out. You can also search in cloudera configuration search tab of your datanode.